1. Field of the Invention
Illustrative embodiments of the present invention relate to a transfer unit and an image forming apparatus, such as a printer, a facsimile machine, and a copier, employing the transfer unit.
2. Description of the Background
Image forming apparatuses are used as copiers, printers, facsimile machines, and multi-functional devices combining several of the foregoing capabilities. One conventional image forming apparatus includes a transfer unit to transfer a toner image from an image carrier onto a recording sheet via a belt member serving as an intermediate transfer body. Typically, the belt member is extended around at least three rollers, such as a driving roller, a tension roller, and a speed control roller. Although only two of the three rollers excluding the speed control roller may be used, generally three or more rollers are used to obtain excellent image quality while suppressing color misalignment between different color toners. However, as the number of rollers increases, the space need for the belt member also expands, preventing satisfying recent market demand for more compact image forming apparatuses.
To meet such demand, one conventional transfer unit has been proposed that includes a bending roller pressed against an outer surface of a belt member looped around a plurality of rollers that bends the belt member toward the interior of the loop. Such a configuration can reduce the size of the belt member loop and, by so doing, provide increased flexibility in designing the layout of those devices that are positioned near the transfer unit.
However, in the conventional transfer unit described above, since the bending roller contacts the outer surface of the belt member, any residual toner remaining on the outer surface of the belt member without being transferred onto a recording medium may be conveyed to the bending roller and adhere to the outer surface of the bending roller.
Further, if such residual toner is fixed on the bending roller, the fixed toner may scratch the outer surface of the belt member when the bending roller and the belt member slide over each other, resulting in image failure and a reduced service life of the belt member.